In various orthopedic and general surgeries, it often is necessary to use penetrating-type implantable fasteners to secure tissue, cartilage, ligaments, sutures, mesh or other artifacts to perisoteum or other dense anatomic structures. A common procedure is the repair of a torn meniscus in which it is desirable to re-attach overlying portions of a torn meniscus to adjacent or underlying meniscus portions. One class of fastening device known in the art may be compared to a staple gun which uses a spring mechanism to drive a fastener distally from the device working end into the anatomic structure, or a reciprocating hammer to repeated drive the fastener. Also, various types deformable fasteners are used in surgeries to attach 1.sup.st and 2.sup.nd tissue layers, such as a biocompatible implantable staple. Such commercially available fastening instruments typically are designed to mechanically deform the malleable leg portions of a wire-form staple by holding a portion of the staple while bending leg portions as the staple is ejected from the distal working end of the instrument. A related type of fastener system captures tissue and drives a deformable fastener by means of a hammer mechanism into an anvil portion, as in an Endo-GIA or circular anastomosis stapler. The fastening instruments of all the types described above are mechanically complex and require many moving parts which results in relatively expensive instruments (e.g., from $100 to $300). Typically, such instruments must be disposable and thus add measurably to the costs of a surgery and cause financial burdens on the health care system.
Besides being expensive, the typical commercially available stapling systems suffer from several other disadvantages. First, a spring-driven mechanical fastener is propelled outwardly and into bone, periosteum, etc., with only a predetermined amount of force that in turn develops a particular rate of staple penetration. The rate may be too slow for the densest anatomic structure, often requiring repeated firings of staples until staple's depth of penetration is adequate. This may lead to time-consuming retrieval and removal of mis-fired staples. Also, the rate of staple penetration may be too fast for less dense anatomic structures leading to collateral tissue damage upon staple firing. When hammer-and-anvil type fastening mechanisms is employed, the thickness of captured tissue may vary widely. Such a system that develops a staple-driving force from a squeeze-type handgrip may not provide the operator adequate control over the power needed to propel the fastener through tissue layers. If the tissues are poorly fastened, for example in an intestinal anastomosis, the fastened site may leak and result in serious complications. Many tissue fastening procedures offer only a single opportunity to develop a secure or leak-proof seal. Another disadvantage of prior art fastener systems is that they cannot be scaled down in size to 2.0 to 5.0 mm. (or smaller) introducers for microsurgeries due to the mechanical complexity and moving parts of the device. Many of the above-described disadvantages relate to the unsophisticated means of delivering mechanical driving forces to the fastener--typically (i) a spring-load mechanism in the introducer or (ii) squeeze grips in a handle that mechanically translate driving forces to the fastener through a moving push-rod.
What is needed is: (1) a surgical fastener system that allows for precise control of the rate at which the fastener penetrates tissue; (2) a surgical fastener system that has very few moving thus making it inexpensive to manufacture; and (3) a surgical fastener that can be miniaturized and delivered from a substantially small introducer (e.g., 1.0 mm. to 3.0 mm. in diameter or cross-section). Besides, the above listed requirements, it would be desirable if the fastener system were suited for disposable introducers or non-disposable introducers.